(1) Field of the Invention
The present invention relates to a multimedia optical disc which stores multimedia data, and to an apparatus and a method for reproducing the multimedia optical disc, more specifically to an improvement in the reproduction of movie applications.
(2) Description of the Prior Art
Currently, laser discs and video CDs (Compact Discs) are known as optical media in which audio information and moving picture information are recorded to be reproduced by dedicated apparatuses.
Laser discs are optical discs with a diameter of about 30 cm storing about an hour of analog moving picture data. Laser discs have been used as media for storing movies or music video works. However, since laser discs are bulky and hard to carry or stock, other media which are more compact than the laser discs have been sought.
Video CDs have achieved the above purpose by enabling moving picture data to be recorded on CDs. The CDs have a diameter of 12 cm and at first were used to store only audio data. The video CDs adopt a digital data compression method called MPEG (Moving Picture Experts Group) which has a high compression rate. The resolution of video CDs is as low as 352×240 though they are compact in size.
The above laser discs and video CDs, on the other hand, have the following limitation on the voice and sub-pictures. That is, since audio information is recorded in a channel, it is impossible to deal with a plurality of languages. Furthermore, the sub-picture data is recorded as a part of moving picture data and it is impossible to deal with a plurality of languages. Therefore, Japanese, English, French, and Germany versions of voices and subtitles for the same moving picture data, for example, cannot be recorded in the above conventional discs.
Different versions of a movie, for example, a theater version, a no-cut version, and a TV on-air version are available. Conventionally, it was possible to record all these versions in a video CD only if the movie was short enough to record in the disc. However, this was not possible for general movie films having 1-2 hours of reproduction time.
A laser disc can store monoaural audio data (analog or digital) in four channels at maximum along with about one hour of analog moving picture data. Laser discs are mainly used for storing movie applications. However, general movies are often about two hours long and sometimes have different versions, namely, a theater version, a TV on-air version, other language versions (voices or subtitles), etc.
It is impossible for a laser disc to store all of such versions since the recording time of the analog moving picture data is limited to about one hour. Even if a laser disc stores audio data in channels along with a plurality kinds of very short moving picture data, the following problems occur:    (1) The plurality kinds of very short moving picture data overlap each other, generating a poor recording efficiency.    (2) If a plurality of subtitles are required, as many pieces of the same moving picture data as the plurality of subtitles must be created since the subtitle is inserted in the moving picture data.    (3) It is not possible for the user to change the current subtitle to another during a reproduction of moving picture data. To reproduce the desired subtitle, the user needs to reproduce a series of moving picture data including the desired subtitle from the beginning. That is, it is not possible for the user to change only the subtitle during a reproduction of moving picture data.    (4) If plurality kinds of moving picture data have different numbers of audio channels for different languages and if a desired language is stored in a plurality of audio channels with different channel numbers, the user needs to change the audio channel number to maintain the desired language each time the user changes the moving picture data.